1. Field of the Invention
The present invention relates to a valve operating system for an internal combustion engine, which uses a rollered cam follower including a pair of support walls which are integrally formed on a cam follower body and arranged in parallel to sandwich a roller therebetween, so that outer peripheries of opposite ends of a roller shaft having the roller rotatably carried thereon are supported in through-bores in the support walls, and particularly, to a valve operating system suitable for an internal combustion engine, which includes a plurality of rollered cam followers disposed adjacent one another and having rollers put into contact with a plurality of cams, respectively, at least a portion of the cam followers being operatively connected to an engine valve, so that the valve operating characteristic of the engine valve can be changed by the movement of a switching pin which is mounted to be slidingly movable astride adjacent cam followers, thereby enabling the connected and disconnected states of the cam followers to be switched over from one to another.
2. Description of the Related Art
The above-described rollered cam follower is designed so that the slidability and the followability with respect to a cam of the cam follower are enhanced by the roller placed in contact with the cam. Such rollered cam follower is conventionally widely used In valve operating systems for Internal combustion engines.
In the conventional rollered cam follower, there are known methods for fixing the roller shaft, for example, to strike and caulk the opposite end faces of the roller shaft with a caulking punch, as shown in Japanese Patent Application Laid-open No.5-321999, and to use a bolt-shaped roller shaft and tighten and fix the shaft end outside the support wall by a nut, as shown in Japanese Utility Model Application Laid-open No.57-98350.
However, when the roller shaft is fixed by caulking, there is a problem that equipment for caulking processing is specially required, resulting in an increase in cost.
When a hollow roller shaft is used, deformation or strain is liable to be produced in the roller shaft due to the caulking. Particularly, when the deformation or strain has been produced in an outer peripheral surface of the roller shaft, certain disadvantages are encountered, such that a roller-rolling face is not smooth and the roller cannot be rotated smoothly on the roller-rolling face. Particularly, when a switching pin capable of connecting the cam followers in order to change the valve operating modes has been slidably fitted In a hollow portion of the roller shaft, the slidability of the switching pin may be injured due to the deformation or strain of the inner peripheral surface of the roller shaft in some cases, whereby the changing of the valve operating modes cannot be performed properly.
On the other hand, when the roller shaft is fixed by the bolt and the nut, the following problem is encountered: The head of the bolt and the nut protrude from the outer surfaces of the support walls, and the width of the cam follower (the maximum dimension in a direction along the roller shaft) is increased more than required. To solve the above problem due to the bolt and the nut, it is conceived to fix the roller shaft in the through-bore in the support wall by use of a resilient fastener such as a circlip. In this case, however, it is desirable that the shape and the disposition of a groove for mounting of the fastener defined in the support wall is taken into a special consideration, so that problems in respect of the strength and the like may not arise despite the defining of the groove.